1. Field of the invention
This invention relates to an air conveyor/accumulator for transporting objects from one location to another and for storing objects between work stations, and, more specifically, to an air conveyor/accumulator having two plenums, one for air transport and one for supplying air to the top deck.
2. Description of the Prior Art
Air conveyors are commonly used for the rapid transport of relatively light objects from one location to another. One typical use of air conveyors is in the transport of empty aluminum or steel cans, for example, from a forming machine to a filling machine.
U.S. Pat. Nos. 3,890,011; 4,392,760; and 4,744,702 are representative of prior art air conveyors. The prior art air conveyors utilize an elongated plenum with a top deck disposed over that plenum. Air is introduced into the plenum using a blower means, such as a fan. Air from the plenum is discharged through a plurality of directional openings in the top deck, thereby creating an air jet that impinges on the objects being conveyed and moves the objects longitudinally along the conveyor.
The fan may be located outside of the plenum and connected thereto through a duct. An example of this configuration is illustrated in U.S. Pat. No. 3,890,011. Alternatively, the fan may be mounted in the plenum, as illustrated in U.S. Pat. No. 4,392,760. The conveyor is typically divided into zones that are closed at each end. Separate fans are provided for each zone.
The designs of the prior art have several drawbacks. First, in order to maintain adequate consistency and control of the speed of objects moving on the conveyor, short zones are required. However, having short zones increases the number of fans required, which increases the overall cost, as distinguished from operational costs, of the conveyor.
A second drawback with prior art designs results when there is a gap in the joints between sections of the top deck. Air conveyors are manufactured in sections and then assembled on site. This results in joints separating sections of the top deck. When the joints fall within a fan zone, they are under air pressure. If there is a gap in the joint, air may be discharged onto the top deck in a vertical stream, perpendicular to the direction in which the objects on the conveyor are traveling. This vertical stream, or "air knife", disrupts object travel on the conveyor. One known way of lessening the risk of "air knife" is to provide interlocking deck joints. However, the use of this type of joint greatly increases installation time compared with conveyors using flat, abutting joints. Moreover, this type of deck joint makes disassembly for maintenance more costly and time consuming because, in order to remove one section of top deck, at least one of the adjacent sections must also be removed to facilitate separation of the interlocking joints.
There remains a need for an air conveyor that has short, controllable pressure zones, yet does not require the use of separate blower means for each zone. In addition, there remains a need for an air conveyor having sections which may be easily and quickly assembled and disassembled, yet having deck joints which are not susceptible to "air knife".